bpo-37685: Fixed __eq__, __lt__ etc implementations in some classes. (GH-14952)

They now return NotImplemented for unsupported type of the other operand.

Lib/tkinter/__init__.py

@@ -484,6 +484,8 @@ class Variable:
         Note: if the Variable's master matters to behavior
         also compare self._master == other._master
         """
+        if not isinstance(other, Variable):
+            return NotImplemented
         return self.__class__.__name__ == other.__class__.__name__ \
             and self._name == other._name
 

Lib/tkinter/font.py

@@ -101,7 +101,9 @@ class Font:
         return self.name
 
     def __eq__(self, other):
-        return isinstance(other, Font) and self.name == other.name
+        if not isinstance(other, Font):
+            return NotImplemented
+        return self.name == other.name
 
     def __getitem__(self, key):
         return self.cget(key)

Lib/tkinter/test/test_tkinter/test_font.py

@@ -1,7 +1,7 @@
 import unittest
 import tkinter
 from tkinter import font
-from test.support import requires, run_unittest, gc_collect
+from test.support import requires, run_unittest, gc_collect, ALWAYS_EQ
 from tkinter.test.support import AbstractTkTest
 
 requires('gui')
@@ -70,6 +70,7 @@ class FontTest(AbstractTkTest, unittest.TestCase):
         self.assertEqual(font1, font2)
         self.assertNotEqual(font1, font1.copy())
         self.assertNotEqual(font1, 0)
+        self.assertEqual(font1, ALWAYS_EQ)
 
     def test_measure(self):
         self.assertIsInstance(self.font.measure('abc'), int)

Lib/tkinter/test/test_tkinter/test_variables.py

@@ -2,6 +2,7 @@ import unittest
 import gc
 from tkinter import (Variable, StringVar, IntVar, DoubleVar, BooleanVar, Tcl,
                      TclError)
+from test.support import ALWAYS_EQ
 
 
 class Var(Variable):
@@ -59,11 +60,17 @@ class TestVariable(TestBase):
         # values doesn't matter, only class and name are checked
         v1 = Variable(self.root, name="abc")
         v2 = Variable(self.root, name="abc")
+        self.assertIsNot(v1, v2)
         self.assertEqual(v1, v2)
 
-        v3 = Variable(self.root, name="abc")
-        v4 = StringVar(self.root, name="abc")
-        self.assertNotEqual(v3, v4)
+        v3 = StringVar(self.root, name="abc")
+        self.assertNotEqual(v1, v3)
+
+        V = type('Variable', (), {})
+        self.assertNotEqual(v1, V())
+
+        self.assertNotEqual(v1, object())
+        self.assertEqual(v1, ALWAYS_EQ)
 
     def test_invalid_name(self):
         with self.assertRaises(TypeError):